This invention relates to an endless metal power transmission chain-belt constructed to interconnect the pulleys of a pulley transmission, as for example, a continuously variable transmission (CVT), especially in a motor vehicle. More particularly the invention relates to a chain-belt constructed of interconnected links and drive or load blocks.
Variable pulley transmissions for automotive use have been suggested for many years. In those transmissions, at least one flange of each pulley is axially movable with respect to the other; as the effective diameter of one pulley is changed, the effective diameter of the other is simultaneously changed in the opposite direction. Thus speed ratio changes are effected continuously in a smooth manner. It is now anticipated that they will soon be widely used in automobiles. They have already been used in some commercial automobiles, such as a Dutch car called the "Daf". In the early constructions, elastomer belts were used to transfer the torque between the drive and driven shafts; the "Daf" car apparently used elastomer belts. In the later cars, a metal belt was used, the belt comprised a carrier and drive or load blocks thereon which drivingly contacted the pulley flanges. Typically the belt used was a "push" belt generally kind taught by the Van Doorne et al patent, No 3,720,113, to be discussed in more detail herein.
The push belt of Van Doorne et al's construction is relatively expensive to manufacture because the nested bands must be precision matched to each other. A "pull" belt in which drive or load blocks are substantially fixedly positioned on a chain or other carrier similar to that taught by Cole et al patent No. 4,313,730, has a substantial cost advantage over the described push belt because the chain links and the load blocks are stamped from sheet stock, the pivot members are cord-wood cut from extruded stock material, and for the most part, assembly is by automatic assembly machines. The Cole et al patent is also discussed in more detail herein.
Aside from costs, a major concern of automotive engineers is noise generation by drive belts for pulley transmissions.
A certain amount of noise is generated when drive blocks engage the flanges of the pulleys, and when the noise manifests itself in a fixed pattern, it is objectionable to humans. Noise of a mixture of frequencies is less objectionable. Automotive engineers rate noise generated by drive belts of the type described herein in a generally subjective manner by driving or riding in an automobile in which the belt is installed and listening to the generated noise. The noise is then rated on a numerical scale of 1 to 10 with the higher numbers indicating the less objectionable noise.